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Re: discussion of LC comments on Extensions

From: Lofton Henderson <lofton@rockynet.com>
Date: Mon, 28 Apr 2003 10:54:03 -0600
Message-Id: <>
To: Mark Skall <mark.skall@nist.gov>
Cc: www-qa@w3.org

[switching thread to www-qa....]

At 10:59 AM 4/28/03 -0400, Mark Skall wrote:

>>>The new Concept chapter will have a DoV caution and we agreed(?) that 
>>>each DoV would have a simple caution statement.
>>I have made an alternate proposal, which has been linked from the issue 
>>list for some time:
>>I disagree that we should "tone it down" -- extensibility is #1 on my 
>>interoperability list of evils.
>Extensibility does not equal DOV.  DOV has to do with variability.  Every 
>technique for variability does not "extend" the standard.  Subsetting, for 
>example, does not extend.  rather it organizes things differently

Hmmm, I'm not quite sure that I understand your point.  Extensibility is 
one of the (current) 8 DoV, and has been such since June 2002.  From "4. 

dimensions of variability
the ways in which different products that are conformant to a specification 
may vary among themselves. In this Specification Guidelines document, the 
dimensions of variability are used to help organize, classify and assess 
the conformance characteristics of W3C specifications

Extensibility certainly fits as one of the ways in which conformant 
products may vary amongst themselves.

My original point was that, while acknowledging the reasons for which specs 
allow extensibility, we should also keep strong caveats about the 
consequences.  In my (direct) experience, there have been few cases (none?) 
in which there is not some interoperability downside, regardless of how 
well justified the use of extensibility might be.  If someone were to offer 
an example (no interop downside), it would be interesting to include.

In the balance, it may indeed be that the benefit of extensibility exceeds 
the cost.

Received on Monday, 28 April 2003 13:05:33 UTC

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